Reading input into an array using getchar() in c

Question

I am writing a function to read character input that has to consume leading white spaces before it begins to address the rest of the inputted line. I successfully read the leading whitespace characters of an input, if they exist. But for the life of me, I cannot figure out when I am getting seg faults when I try to read the rest of the line. I am using ansi C. Here is my code:

    void readCharLine(char **line_address) {
        int c;
        int index = 0;
        *line_address = malloc(35 * sizeof(char));
        c = getchar();

        /*Consume white spaces*/
        while ((c == ' ') && (index < 35)) {
            c = getchar();
            index++;
        }

        c = getchar();

        /*read rest of line*/
        while(c != '\n') {  
            *line_address[index] = c;
            c = getchar();
            index++;
        }
    }

I call readCharLine as follows:

    readCharLine(&node -> input);

where node is a struct declared as follows:

    /*Node declaration*/
    typedef struct {
        char *input;
        struct Node *next;
    } Node;

Thank you!

Note that you throw away the first (possibly only) non-blank character. You also need to test for EOF (you're using int c; which is good — it allows you to test reliably for EOF). You may want to look at <ctype.h> and isspace() or isblank(). — Jonathan Leffler
– Jonathan Leffler, Commented Feb 18, 2016 at 3:20

John3136 · Accepted Answer · 2016-02-18 03:08:49Z

1

Your are incrementing index even for the chars you discard, so chances are you are writing off the end of the array.

You probably also want while(c != '\n') { to be while(index < 35 && c != '\n') { - adjust as required depending on whether you need to 0 terminate the string.

answered Feb 18, 2016 at 3:08

John3136

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